What horse is bettter for beginner a quarter horse or a paint horse?

The breed matters little. The horse is what really matters. Whether it is a Shire or a Shetland, a paint or a quarter horse, you want an older, calm, well trained horse that has plenty of experience in the disipline you want to try.

The breed or size doesn't matter- it's the heart and willingness of the horse to partner with you and keep you safe and allow you to learn and improve.

Also, a Paint horse is likely to be genetically very similar to a Quarter Horse, since the Paint breed is a color breed that was derived from the Quarter Horse.